Cumene decomposition

Cumene decomposition rate law if desorption were limiting... 

However, from runs 1 and 2 we observe that a fourfold increase in the pressure of methane has little effect on —r. Consequently, we assume that methane is either very weakly adsorbed (i.e., KyiPyi 1) or goes directly into the gas phase in a manner similar to propylene in the cumene decomposition previously discussed. 

Cumene interacts more strongly than benzene with zeolite OH groups. At higher temperatures cumene decomposition is revealed by the formation of surface species similar to those found for propene. 

These three steps represent the meehtmisTTi For cumene decomposition... 

The Course of the Cumene Decomposition Reaction Over Acidic Catalyst... 

If the cumene decomposition is adsorption rate limited, then the initial rate will be linear with the initial partial pressure of cumene, as shown in Figure 10-15. 

The forward cumene decomposition reaction is a single-site mechanism involving only adsorbed cumene, while the reverse reaction of propylene in the gas phase reacting with adsorbed benzene is an Eley-Rideal mechanism. 

The thermal decomposition of thia2ol-2-yl-carbonyl peroxide in benzene, bromobenzene, or cumene affords thiazole together with good yields of 2-arylthiazoles but negligible amounts of esters. Thiazol-4-ylcarbonyl peroxide gives fair yields of 4-arylthiazoles, but the phenyl ester is also a major product in benzene, indicating reactions of both thiazol-4-yl radicals and thiazol-4-carbonyloxy radicals. Thiazole-5-carbonyl peroxide gives... 

Sales demand for acetophenone is largely satisfied through distikative by-product recovery from residues produced in the Hock process for phenol (qv) manufacture. Acetophenone is produced in the Hock process by decomposition of cumene hydroperoxide. A more selective synthesis of acetophenone, by cleavage of cumene hydroperoxide over a cupric catalyst, has been patented (341). Acetophenone can also be produced by oxidizing the methylphenylcarbinol intermediate which is formed in styrene (qv) production processes using ethylbenzene oxidation, such as the ARCO and Halcon process and older technologies (342,343). 

Other Hydroperoxides. Several hydrotrioxides including alkyl hydrotrioxides, R—OOOH, have been reported (63,64). There is strong spectroscopic evidence that a-cumyl hydrotrioxide [82951-48-2] is produced in the low temperature ozonization of cumene. Homolytic decomposition of a-cumyl hydrotrioxide in cumene/acetone-hindered phenol resulted in cumyl alcohol as the only organic product (65). Based on the... 

The most widely used process for the production of phenol is the cumene process developed and Hcensed in the United States by AHiedSignal (formerly AHied Chemical Corp.). Benzene is alkylated with propylene to produce cumene (isopropylbenzene), which is oxidized by air over a catalyst to produce cumene hydroperoxide (CHP). With acid catalysis, CHP undergoes controUed decomposition to produce phenol and acetone a-methylstyrene and acetophenone are the by-products (12) (see Cumene Phenol). Other commercial processes for making phenol include the Raschig process, using chlorobenzene as the starting material, and the toluene process, via a benzoic acid intermediate. In the United States, 35-40% of the phenol produced is used for phenoHc resins. 

This procedure has also been used successfully in the acetylation of cumene and fert.-butyl benzene. At the low temperatures employed there is very little decomposition, as is shown by the small amount of high-boiling residue. 

A common deposition reaction combines the metal chloride with a hydrocarbon, such as butane, at an optimum deposition temperature of 1000°C.9 1 Other hydrocarbons can also be used. Another useful reaction is the decomposition of the chromium di cumene Cr[(C6H5)C3H7]2 in atemperature range of 300-550°C and at pressures of 0.5-50 Torr.0 1... 

Induced reactions involving hydrogen peroxide can be observed with hydrogen peroxide derivatives, as well. For instance, the reaction between cumene hydroperoxide and iron(IT), in the absence of oxygen, results in a considerable induced decomposition of the peroxy compound, while, in the presence of oxygen, a marked oxidation of iron(II) takes place s . 

A very similar rearrangement takes place during the acid-catalysed decomposition of hydroperoxides, RO—OH, where R is a secondary or tertiary carbon atom carrying alkyl or aryl groups. A good example is the decomposition of the hydroperoxide (84) obtained by the air-oxidation of cumene [(l-methylethyl)benzene] this is used on the large scale for the preparation of phenol and acetone ... 

Chain decomposition of ozone was also observed in the oxidation of cumene by an O3-O2 mixture [151]. The rate of ozone consumption was found to be... 

The decomposition of carboxyl radical occurs very rapidly, and C02 is formed with a constant rate in the initiated co-oxidation of cumene and acid [104]. 

The increase in the amount of catalyst introduced in oxidized cumene (353 K) increases the oxidation rate, decreases the amount of the formed hydroperoxide, and increases the yield of the products of hydroperoxide decomposition methylphenyl ethanol and acetophenone. Similar mechanism was proposed for catalysis by copper phthalocyanine in cumene oxidation [254],... 

The effect of jumping of the maximal hydroperoxide concentration after the introduction of hydrogen peroxide is caused by the following processes. The cumyl hydroperoxide formed during the cumene oxidation is hydrolyzed slowly to produce phenol. The concentration of phenol increases in time and phenol retards the oxidation. The concentration of hydroperoxide achieves its maximum when the rate of cumene oxidation inhibited by phenol becomes equal to the rate of hydroperoxide decomposition. The lower the rate of oxidation the higher the phenol concentration. Hydrogen peroxide efficiently oxidizes phenol, which was shown in special experiments [8]. Therefore, the introduction of hydrogen peroxide accelerates cumene oxidation and increases the yield of hydroperoxide. 

The experiments on emulsion cumene oxidation with AIBN as initiator proved that oxidation proceeds via the chain mechanism inside hydrocarbon drops [17]. The presence of an aqueous phase and surfactants compounds does not change the rate constants of chain propagation and termination the ratio (fcp(2fct)-1/2 = const in homogeneous and emulsion oxidation (see Chapter 2). Experiments on emulsion cumene oxidation with cumyl hydroperoxide as the single initiator evidenced that the main reason for acceleration of emulsion oxidation versus homogeneous oxidation is the rapid decomposition of hydroperoxide on the surface of the hydrocarbon and water drops. Therefore, the increase in the aqueous phase and introduction of surfactants accelerate cumene oxidation. 

The kinetic study of cumyl hydroperoxide decomposition in emulsion showed that (a) hydroperoxide decomposes in emulsion by 2.5 times more rapidly than in cumene (368 K, [RH] [H20] = 2 3 (v/v), 0.1 N Na2C03) and (b) the yield of radicals from the cage in emulsion is higher and close to unity [19]. The activation energy of ROOH decomposition in cumene is Ed = 105 kJ mol-1 and in emulsion it is lower and equals Ed 74 kJ mol 1 [17]. 

Phenol formed in the system due to acid-catalyzed decomposition of hydroperoxide retards the cumene oxidation. The aqueous phase withdraws phenol from the hydrocarbon phase. This is the reason why the emulsion oxidation of cumene helps to increase the yield of hydroperoxide. The addition of hydrogen peroxide into the system helps to increase the yield of hydroperoxide. 

Phenol is the major source of Bakelite and phenol resins, which are utihzed in many commodities worldwide phenol is also used as reagent for syntheses of dyes, medicines and so on. The industrial demand for phenol has increased every year and its production now exceeds 7.2 megaton year 94% of the worldwide production of phenol is processed in the cumene process. The cumene process involves the reaction of benzene with propene on acid catalysts like MCM-22, followed by auto-oxidation of the obtained cumene to form explosive cumene hydroperoxide and, finally, decomposition of the cumene hydroperoxide to phenol and acetone in sulfuric acid (Scheme 10.3) [73],... 

Combining thianthrene radical ion(l+) with free radicals to produce thianthrenium salts has also been achieved. Decomposition of various cumene hydroperoxides (83MI6) and of azobis(2-phenoxy-2-propane) (85MI1) gave 5-arylthianthrenium ions together with 5-(propen-2-yl)thianthrenium perchlorate in the latter case. 

While some phenol is produced by the nucleophilic substitution of chlorine in chlorobenzene by the hydroxyl group (structure 17.17), most is produced by the acidic decomposition of cumene hydroperoxide (structure 17.18) that also gives acetone along with the phenol. Some of the new processes for synthesizing phenol are the dehydrogenation of cyclohexanol, the decarboxylation of benzoic acid, and the hydrogen peroxide hydroxylation of benzene. 

Ed, the activation energy for thermal initiator decomposition, is in the range 120-150 kJ mol-1 for most of the commonly used initiators (Table 3-13). The Ep and Et values for most monomers are in the ranges 20-40 and 8-20 kJ mol-1, respectively (Tables 3-11 and 3-12). The overall activation energy Er for most polymerizations initiated by thermal initiator decomposition is about 80-90 kJ mol-1. This corresponds to a two- or threefold rate increase for a 10°C temperature increase. The situation is different for other modes of initiation. Thus redox initiation (e.g., Fe2+ with thiosulfate or cumene hydroperoxide) has been discussed as taking place at lower temperatures compared to the thermal polymerizations. One indication of the difference between the two different initiation modes is the differences in activation energies. Redox initiation will have an Ed value of only about 40-60 kJ mol-1, which is about 80 kJ mol-1 less than for the thermal initiator decomposition [Barb et al., 1951], This leads to an Er for redox polymerization of about 40 kJ mol-1, which is about one half the value for nonredox initiators. 

Chain Termination in the Oxidation of Cumene. Traylor and Russell (35) assume that the acceleration in the rate of oxidation of CH which is produced by added COOH is solely caused by a chain transfer reaction between CO radicals and COOH. This assumption implies that all CH3OO radicals enter into termination via Reaction 13. However, Thomas (32) has found that acetophenone is formed even in the presence of sufficient COOH to raise the oxidation rate of CH to its limiting value. (The receipt of Thomas manuscript prior to publication stimulated the present calculations.) From this fact, and from a study of the acetophenone formed during the AIBN-induced decomposition of COOH, Thomas concludes that the accelerating effect of added COOH is primarily caused... 

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